After a years long letter campaign, for one special day I was named by parliament as a celebratory envoy to Palestine, for the express purpose of cursing at Lectro. Now you know.
Regarding your "red flags" - calling an entire political party anti-semitic for their political criticisms of a foreign state and that states political influence on their own country, is not "raising red flags". The inability and unwillingness of certain people, gentile and Jew alike, to differentiate between the political state of Israel and the religion of Judiasm, is nearly the entire problem. 25% of Israelites aren't Jewish. Benjamin Netanyahu and the Likud party are not religious figureheads. The Torah does not call for Palestinians to be held prisoner on their own land.
I provided a direct public source from the Labour Friends of Israel, the group to which the Labour defectors belong, where they refer to "anti-zionism" as "anti-semitic". In terms of religious tolerance and foreign policy, Zionism is radical and Islamaphobic.